The independent investigation commissioned by Fifa into allegations that Mohamed bin Hammam paid bribes to officials during his campaign to unseat Sepp Blatter as Fifa president has uncovered further evidence against the Qatari. A total of nine Caribbean Football Union associations are believed to have told investigators they were offered $40,000 (£25,000) in brown paper envelopes.

A leaked preliminary report, on which the decision to suspend Bin Hammam and Fifa's then vice-president Jack Warner was taken on 29 May, had relied on evidence from four CFU members – the Bahamas, Bermuda, Cayman Islands and the Turks & Caicos Islands. A further five associations – Puerto Rico, Surinam, Grenada, Aruba and Curacao – have since told the investigation headed by the former FBI director Louis Freeh that they too were offered or given money at the meeting on 10-11 May, or saw evidence of that happening.

The investigation by Freeh was concluded last week and also included evidence that the CFU did not have the means to make the payments itself.

The CFU's financial statement for the end of 2010 reveals it had net debts of $242,000, including $376,000 owed to Warner – who had been the CFU president – for a loan he made to the organisation.

A total of $1m is alleged to have been offered to the 25 member associations that attended the specially convened meeting. CFU officials are alleged to have handed over the money to them one by one in brown envelopes. Warner, who has since resigned as a Fifa vice-president while protesting his innocence, is alleged to have told them the next day that it was from Bin Hammam.

The report compiled by Robert Torres, the judge heading the Fifa ethics committee investigation, has been sent to Bin Hammam and the two accused CFU officials – Debbie Minguell and Jason Sylvester – ahead of a meeting in Zurich on 22 and 23 July.

Bin Hammam, who has continued to insist that he did nothing wrong, is expected to argue that some of those who claim to have been offered money did not even have a vote in the presidential election. He will also argue that the evidence shows he was not present when the money was handed over and stress that Warner has not claimed it was from him.

After the original report from the ethics committee, which found "comprehensive, convincing and overwhelming evidence" of a prima facie case that Bin Hammam had paid or offered the cash, was leaked the Asian Football Confederation chief said: "There is nothing I can say more than I deny the allegations and insist that I have not done anything wrong during special Congress at Trinidad."

Around 12 associations in the Caribbean did not meet the investigators, and neither did Warner, although when he resigned he promised to co-operate with the inquiry. Fifa could now open ethics committee investigations into the actions of those associations.

Fifa has invited Bin Hammam, Sylvester and Minguell to present their position in person to the ethics committee. Both sides are able to call witnesses.